{% comment %} toc(source, class, list_number) {% endcomment %}
{% include _helper/_toc.html source=source level=1 number_prefix='' %}
{% assign toc = _toc | normalize_whitespace %}
{% if toc.size != 0 %}
  {% capture toc %}
    <ol class={{ class }}>
      {{ toc }}
    </ol>
  {% endcapture %}
{% endif %}
